Actuator drive device
View Patent ↗An actuator drive device is configured to drive an actuator. The actuator drive device includes a storage section for storing a drive condition of the actuator, a processor for calculating and outputting drive signal D(t) based on a drive base signal V(t) calculated based on the drive condition with respect to time t, and a generator for outputting, based on the drive signal D(t) calculated, a driving signal for driving the actuator. The drive base signal V(t) is a sum of a fundamental wave and at least one harmonic wave of the fundamental wave. The processor is operable to determine the coefficient a k such that the drive base signal V(t) changes linearly from a minimum value to a maximum value with respect to a time. This actuator drive device improves the linearity of the driving of the actuator.
1. An actuator drive device configured to drive an actuator which includes a driver and a drive electrode, said actuator drive device comprising:
a storage section for storing a drive condition of the actuator;
a processor for calculating and outputting drive signal D(t) based on a drive base signal V(t) calculated based on the drive condition with respect to time t; and
a generator for outputting, based on the drive signal D(t) calculated, a driving signal to the drive electrode of the actuator for driving the driver of the actuator,
wherein the actuator drive device is configured to drive the actuator in a main mode while not exciting the actuator in a mode different from the main mode,
wherein the drive base signal V(t) is a sum of a fundamental wave and at least one harmonic wave of the fundamental wave, and is expressed as:
V
(
t
)
=
A
∑
k
=
1
N
a
k
sin
(
2
π
f
base
kt
)
,
with an amplitude A, an integer N, a coefficient a k , a frequency f base of the fundamental wave, and an integer k (1≦k≦N),
wherein frequencies of the fundamental wave and the at least one harmonic wave of the fundamental wave includes a resonance frequency f 0 of the main mode,
wherein the mode, different from the main mode, is excited with a vibration at a resonance frequency f 1 ,
wherein an upper limit frequency out of the frequencies of the fundamental wave and the at least one harmonic wave of the fundamental wave is a frequency f BW ,
wherein a frequency kf base of a harmonic wave out of the at least one harmonic wave at any order k is included within a range of f base ≦kf base ≦f BW ≦f 1 , and
wherein the processor is operable to determine the coefficient a k such that the drive base signal V(t) changes linearly from a minimum value to a maximum value with respect to a time.
2. The actuator drive device according to claim 1 , wherein the processor outputs the drive base signal V(t) as the drive signal D(t).
3. The actuator drive device according to claim 1 , wherein the drive signal D(t) is expressed as:
D ( t )= V ( t )+ X,
with the drive base signal V(t) and a bias X.
4. The actuator drive device according to claim 1 ,
wherein an evaluation function S is expressed as:
S
=
∑
T
/
2
-
Δ
t
T
/
2
+
Δ
t
V
(
t
)
-
(
mt
+
n
)
2
with a period T(=1/f base ) of the drive base signal V(t), a duration Δt which is a half of a duration from the minimum value to the maximum value, and integers m and n, and
wherein the coefficient a k is determined to satisfy S/N S <0.0015 with a discrete value N S of the time t.
5. The actuator drive device according to claim 1 ,
wherein an evaluation function S is expressed as:
S
=
∑
T
/
2
-
Δ
t
T
/
2
+
Δ
t
V
′
(
t
)
-
m
2
with a period T(=1/f base ) of the drive base signal V(t), a duration Δt which is a half of a duration from the minimum value to the maximum value, and an integer m, and
wherein the coefficient a k is determined to satisfy S/N S <6 with a discrete value N S of the time t.
6. The actuator drive device according to claim 1 ,
wherein an evaluation function S is expressed as:
S
=
∑
T
/
2
-
Δ
t
T
/
2
+
Δ
t
V
″
(
t
)
2
with a period T(=1/f base ) of the drive base signal V(t) and a duration Δt which is a half of a duration from the minimum value to the maximum value, and
wherein the coefficient a k of the harmonic wave is determined to satisfy S/N S <1100 with a discrete value N S of the time t.
7. The actuator drive device according to claim 1 ,
wherein a highest frequency Nf base of the at least one harmonic wave is a frequency f BW , and
wherein the frequency f BW is determined by:
A d ( f BW )> A u ( f BW )+3 dB,
with an amplitude characteristic A d (f) (dB) of a main mode of the actuator with respect to a frequency f, and an amplitude characteristic A u (f) (dB) of an undesired mode of the actuator with respect to the frequency f.
8. The actuator drive device according to claim 7 , wherein the frequency f BW is 1200 Hz.
9. The actuator drive device according to claim 1 ,
wherein components of the drive base signal V(t) is expressed as:
a k sin(2π f base kt ), and
wherein at least one predetermined component of the components is removed from the drive signal D(t).
10. The actuator drive device according to claim 1 , wherein the processor is operable to correct the coefficient a k in response to an ambient temperature of the actuator as to calculate the drive signal D(t).
11. The actuator drive device according to claim 1 , wherein the processor is operable to correct the coefficient a k in response to a vibration of the actuator as to calculate the drive signal D(t).
12. The actuator drive device according to claim 1 ,
wherein the drive signal D(t) is expressed as:
D
(
t
)
=
A
∑
k
=
1
N
b
k
sin
(
2
π
f
base
kt
+
θ
k
)
with a coefficient b k and a phase θ k , and
wherein the processor is operable to correct the coefficient a k in response to a vibration of the actuator as to calculate the coefficient b k and the phase θ k .
13. The actuator drive device according to claim 12 , wherein the processor is operable to correct the coefficient b k and the phase θ k in response to an ambient temperature of the actuator.
14. The actuator drive device according to claim 1 ,
wherein the drive signal D(t) is expressed as:
D
(
t
)
=
A
∑
k
=
1
N
b
k
sin
(
2
π
f
base
kt
+
θ
k
)
with a coefficient b k , a phase θ k , and a bias X, and
wherein the processor is operable to correct the coefficient a k in response to a vibration of the actuator as to calculate the coefficient b k and the phase θ k .
15. The actuator drive device according to claim 14 , wherein the processor is operable to correct the coefficient b k and the phase θ k in response to an ambient temperature of the actuator.
16. The actuator drive device according to claim 1 ,
wherein the drive signal D(t) is expressed as:
D
(
t
)
=
A
∑
k
=
1
N
b
k
sin
(
2
π
f
base
kt
+
θ
k
)
with a coefficient b k , and
wherein the processor is operable to correct the coefficient a k in response to a vibration of the actuator as to calculate the coefficient b k .
17. The actuator drive device according to claim 16 , wherein the processor is operable to correct the coefficient b k in response to an ambient temperature of the actuator.
18. The actuator drive device according to claim 1 ,
wherein the drive signal D(t) is expressed as:
D
(
t
)
=
A
∑
k
=
1
N
b
k
sin
(
2
π
f
base
kt
)
+
X
with a coefficient b k and a bias X, and
wherein the processor is operable to correct the coefficient a k in response to a vibration of the actuator as to calculate the coefficient b k .
19. The actuator drive device according to claim 18 , wherein the processor is operable to correct the coefficient b k in response to an ambient temperature of the actuator.
20. The actuator drive device according to claim 1 , wherein the processor is operable to determine the coefficient a k such that:
the drive base signal changes linearly from a minimum value to a maximum value with respect to a time for a predetermined duration within a period of the fundamental wave; and
the drive base signal changes not linearly from the minimum value to the maximum value with respect to a time for at least a part of a duration within the period of the fundamental wave other than the predetermined duration.